不是连接词是介词短语，通常作状语by now是现在完成时的标志，另外还有so far，till/until now,up to now。

都使⽤现在完成时。如:By now you will have guessed that Im back in Ireland.你现在应该已经猜出我回到了爱尔兰了。He would have been there by now if had not missed the train.如果不是误了⽕车的话他已经到达爱尔兰了类似的还有:even now即使如此, 尽管这样now and then (=every once in a while)不时, 时而, 偶而now and again (=every once in a while)不时, 时而, 偶而every now and then (=every once in a while)不时, 时而, 偶而every now and again (=every once in a while)不时, 时而, 偶而for now[口]暂时, 目前, 眼下from now on从现在起, 今后